We have recently fabricated continuous semiconducting micro and nanowires within the empty spaces of highly ordered microstructured (e.g., photonic crystal or holey) optical fibers (MOF's). These systems contain the highest aspect ratio semiconductor micro- and nanowires yet produced by any method: centimeters long and ~100 nm in diameter. These structures combine the flexible light guiding capabilities of an optical fiber with the electronic and optical functionalities of semiconductors and have many potential applications for in-fiber sensing, including in-fiber detection, modulation, and generation of light.